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red fuzz ( calling Mark Hammer)

8/29/2004 9:46 AM
red fuzz ( calling Mark Hammer)
Hi there,  
Some time ago I built a red fuzz (project on JD sleep's site) and it works great but recently I put it into a box and now I hear some oscillation at the more severe fuzz settings. It was there probably all the time but I didn't notice it till now.  
This happens quite often ,when you have built a project you're very enthusiastic and this makes you less critical so when the first enthusiasm has worn off these things become more apparent  
It's the sort of oscillation that influences the tone in a bad way (parasitic)not a real squeal. What can I do to get rid of it ?  
I would be grateful if you could help me .  
Thanks in advance  
9/1/2004 3:09 PM
Stephen Giles
Yes - it's what we we call in England "sod's law". This may call for a small capacitor, say 100p between the non inverting input and the output of each op amp. I'm only guessing here (at London Heathrow)but try it and see if it makes any difference.  
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9/1/2004 3:11 PM
Stephen Giles
oops - 2 we should be 1 we!!!!
9/1/2004 3:37 PM

Thanks for your reply Stephen , I'll give it a try .  
Things have been very quiet over here on this site lately. Where's everybody gone ??  
9/4/2004 11:43 PM
John Fisher

It sounds like your layout might have something to do with it.  
especially with circuits with high gain, if the output wires are too close to the input wires and especially if they are not shielded you could have a problem like that. it also helps to have the leads to pots and switches only as long as necessary.  
I also built the red fuzz and I like it a lot.  
John Fisher
9/5/2004 2:50 PM
John ,you might have a point there, I didn't use shielded wire .  
I'll change it as soon as possible and will let you know what happened.  
Regards Alf
9/7/2004 4:47 PM
Mark Hammer
I'm back
Sorry I didn't respond. Took my first family vacation ever and was generally incommunicado.  
Our good buddy John seems to have everything in hand though. Caps in feedback loops are often a very good thing for not only keeping oscillations at bay, but also for keeping the fuzz in and the fizz out.
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